A thin film obtained by stacking an ITO thin film and a molybdenum thin film is used as part of an electrical circuit of a liquid crystal display or other electric devices. It is known that, when a molybdenum thin film is formed on an ITO thin film, internal stress is generated in each of the formed thin films, causing the films to be peeled off or broken. The internal stress is divided into two stresses; tensile stress and compression stress. Here, the tensile stress is stress generated in a thin film when the formed film surface is depressed, and the compression stress is stress generated in a thin film when the formed film surface is projected. Normally, an ITO film is subjected to compression stress and a metal thin film (especially a molybdenum thin film) is subjected to tensile stress. If these thin films are stacked under such stresses, these thin films eventually peel off or break, since not only the type of stress is different (compression and tensile), but also the degree of difference in stress becomes large between compression stress and tensile stress, thereby causing a significant degree of warping to be generated at the interface.
As stated above, due to poor adhesiveness between an ITO thin film and a molybdenum thin film, these films are cracked or broken. Since the ITO film was thick, a reverse taper occurs after etching. When an amorphous ITO (a-ITO) is formed, the a-ITO is polycrystallized by heating at a postbake process or at a SiNx film formation process by a CVD method after etching. Since the polycrystallized ITO has poor adhesiveness with a molybdenum film, cracking or breakage of these films occurs. Such cracking and breakage increases defectiveness in products and decreases production yield (Patent Document 1).
In order to solve the above-mentioned problem, a method is disclosed in which complicated steps are combined to produce a multilayer film which is free from peeling and breakage. This method is, however, disadvantageous since production yield is lowered due to increased production steps (Patent Document 2).
For example, in a polycrystalline ITO (p-ITO) method, a multilayer body is produced by depositing a p-ITO film using a vacuum sputtering apparatus, etching the resulting ITO film, depositing a film of molybdenum thereon by means of a sputtering apparatus, and etching the resulting molybdenum film. This method is complicated since film deposition and etching are repeated twice, and hence suffers from poor productivity.
Under such circumstances, a technique has been demanded in which the processes of film formation and etching can be simplified while preventing cracking and breakage of an ITO thin film and a molybdenum thin film caused by stress between the films.
Patent Document 1: JP-A-10-253992
Patent Document 2: JP-A-2005-62889
The invention has been made in view of the above-mentioned problem. An object of the invention is to provide a multilayer structure which contributes to a decrease in product defectiveness ascribable to cracking between or breakage of wiring materials, as well as to improvement of production yield.
Another object of the invention is to provide an electrode for an electrical circuit comprising the above-mentioned multilayer structure.
A further object of the invention is to provide an electric device comprising the above-mentioned multilayer structure or the above-mentioned electrode for an electrical circuit.